The long-term goal of these studies is to molecularly characterize the action of important in vivo targets of ethanol in the nervous system that contribute to intoxication and addiction. Forward genetic screens in C. elegans have identified several key in vivo targets of ethanol that are required for intoxication. Most strikingly, the majority of the intoxicating effects of acute ethanol application in C. e/egans appear to be mediated via the ortholog of the human large-conductance potassium (BK) channel called SLO-1. Electrophysiological analyses found that ethanol potentiates the activity of the BK channel in vivo. The ethanol-induced increase in potassium efflux through the BK channel would cause a decrease in neuronal excitability, which may explain much of the depressive effects of ethanol on behavior. By combining the powerful genetic and molecular techniques of C. e/egans together with patch-clamp recording, the precise mechanism for how ethanol produces intoxication via the BK channel in vivo will be examined. This work will attempt to elucidate the site of ethanol action on the BK channel through site-directed and random mutagenesis of the channel. Studying mutants that are abnormally sensitive to ethanol may also identify proteins that interact with the BK-channel pathway to produce intoxication. Determination of the fundamental molecular mechanisms of ethanol action through the BK channel may provide a basis for a directed approach to design therapeutics to treat the detrimental effects of alcohol.